1. Field of the Invention
The present invention relates to an image processing system which reads an image on an original document, processes the image data as read, and outputs the image in the form of a hard copy.
2. Discussion of the Prior Art
An image processing system which electronically copies a plurality of original documents in a predetermined order of pages, and outputs the copies is known in the art. This copy process will be referred to as a recirculating document handling (RDH) function. A schematic illustration of a conventional image processing system using this copy process is shown in FIG. 7.
In FIG. 7, image data output from an image reading section 51 is first stored in a page memory 53 of a storage unit 52. Generally, the storage unit 52 has a large memory storage capacity in order to store image data representing a number of document pages. Accordingly, a magnetic memory device, such as a hard disk 54, is used in the storage unit 52. A typical access time for the hard disk 54 is approximately 1M byte/sec.
Usually, the hard disk access time is not equal to the transfer rate of input image data provided by the image read section. To compensate for the time difference between these two data transfer rates, the page memory 53 is provided. Image data, temporarily stored in the page memory 53, is sequentially transferred to and stored on the hard disk 54. After image data of a preset number of documents has been stored on the hard disk 54, the image data is then read from the hard disk, and stored again in the page memory 53. After a preset amount of image data has been stored in the page memory 53, the image data is synchronously read from the page memory 53 at a data processing rate defined by the image recording section 55, and transferred to the image recording section 55. Finally, the image record section 55 outputs hard copies of the original documents.
According to this process, the image processing system reads image data corresponding to a number of original document pages, stores the image data on the hard disk 54, and sequentially reads the image data from the hard disk 54 in the page order of the original documents. Consequently, the image processing system can copy a desired number of document pages in a desired order. In other words, the image processing system is capable of electrically performing the RDH function. This function simplifies the work required to produce finished document copies once the ordered pages have been output.
There are several types of document images, such as monochromatic character, monochromatic photograph which requires expression in a multiple of gradations, and color. The RDH function is typically applied to original documents containing a variety of different image types. However, in the image processing system shown in FIG. 7, the read function of the image data and the structure used to store the read image data are fixed irrespective of the image type appearing on individual document pages. The copy mode or image data read structure can be set for the image processing system only on a job or batch basis. Accordingly, the image processing system will operate as set forth in the following examples.
If an original document consists of a single sheet of color text and multiple sheets of monochromatic character text, a color copy mode must nonetheless be selected. If a sheet requiring halftone expression, such as photograph, is contained in an original document, a copy mode capable of halftone expression must be selected. As a result of selecting these various modes, the time and resources required to process each page of the original document is significantly increased regardless of the actual image type on an individual page being processed. The image processing system is, thus, inefficiently used. Specifically, in the first example where the color copy mode was selected, the image processing system will execute color processing for each page of the document. However, no color processing is required for the multiple pages containing monochromatic character text and the additional time required for color processing these pages will be wasted. In the second example where the halftone copy mode was selected, the halftone expression is unnecessary for the pages of monochromatic character text, but will nevertheless be executed, and time and resources, such as toner, will be wasted.